Effect of various catalysts on the chemical structure of oils and asphaltenes obtained from the hydroliquefaction of a highly volatile bituminous coal

Abstract

The catalysts studied were aerosols of SiO 2, Fe 2O 3, MoO 3 and Ni-Mo/Al 2O 3. The hydroliquefaction runs at 350, 400 and 430°C, in the presence of tetralin and sulfur, were evaluated by solvent extractions, hydrogen consumption and structural analysis of the isolated oil and asphaltene fractions. At 350°C, a clear influence of the catalyst on the extraction yields is observed. This effect disappears at higher temperatures. Nevertheless, hydrogen consumption from gas or solvent is affected by the nature of the catalyst at a given temperature. The influence of the catalyst is also confirmed by electron spin resonance study of the stable radicals of the tetrahydrofuran insoluble fractions. After elimination of tetralin, the structural analyses were carried out by gas chromatography (oils), size exclusion chromatography (oils and asphaltenes) and extrography (raw hydroliquefaction products). The oils obtained with sulfided Fe 2O 3 or MoO 3 contained significantly more two-ringed aromatic compounds than oils obtained with the other catalysts or without added catalyst. No significant influence of the catalyst at a given temperature on the oils and asphaltenes is observed by size exclusion chromatography. In contrast, a large temperature effect is evidenced for each fraction, independently of the nature of the catalyst.